This comment is for all of you, who are wondering where the avatar images for different user posts in the internal guestbook (comment & rating) are come from, because I couldn't find it in the X5 documentation. X5 uses the quite popular Gravatar engine (gravatar.com), which links an public E-Mail address of an registered user, to its associated image. If an user E-mail address isn't found, the engine random selects one of the standard icons of the gravatar library, like in the picture below. Therefore the E-mail address in the guestbook object is required too and not optional. If you need to answer user posts, maybe its a good idea to link the webmaster e-mail to a company logo etc., which always stays the same for the whole internet.